Counter-rotation is used in mechanisms which require reversing the angular direction of rotation, in cases in which it is necessary for the driving shaft to rotate in one angular direction, and the other shaft, which is driven by the driving shaft, to rotate in the opposite angular direction. Such forms of transmission are used in helicopter drives, differential transmissions in vehicles, propeller driven marine vessels, turbine engines, turbo-generators, and compressors, to name a few.
Solving the problem of mechanical counter-rotation with a transmission ratio of 1 to 1 and shafts aligned along a common rotational axis is exclusively confined to types of planetary gear transmissions and transmission of torque via gears. The transmission ratio 1 to 1 (1:1) means that an angular displacement at one end of a device is transmitted by the device so that exactly the same angular displacement is produced at the other end of the same device. For example, a solution with a double propeller helicopter with a common axis by S. P. Vaughn (U.S. Pat. No. 2,037,745) where counter-rotation of two propeller systems is used to provide a more stable flight and facilitate the control of the helicopter. A solution with a counter-rotating double propeller system (U.S. Pat. No. 4,642,059) is used for a marine drive, in which case an inner shaft is at one end directly coupled to an outer hollow drive shaft. Another patent (U.S. Pat. No. 4,963,108) describes a system for counter-rotation comprising a propeller with a large gear driven by an engine, with which gear a plurality of smaller gears are in operational contact at its perimeter, so that counter-rotation of the second, driven, shaft is obtained. The known solutions which use planetary geared transmission are cumbersome, with significant losses to friction, accompanied by common problems of wear and low efficiency, due to gaps that cannot be avoided in such solutions. These solutions are also known to produce clattering and loud noise resulting from the existence of the gaps. Such transmission systems also have a low degree of safety of operation, and are known to lack a constant torque at each point. Also, in solutions with planetary gears, the load is unevenly distributed; in most cases concentrated at one point (the point of immediate contact of the driving and driven parts of the assembly). This uneven load distribution creates critical elements in the assembly and requires excessively large parts to provide the necessary safety margins.
The problem of obtaining counter-rotation of coupled shafts with a transmission ratio of 1:1 and shafts aligned along the same rotational axis in the manner disclosed here has not been observed in any other solution known in prior art.